The purpose of this study is to develop techniques for studying central nervous system monoamine metabolism in man, and to assess the value of peripheral neurotransmitter measures as indices of central function. Clinical studies assessing the influence of plasma 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) on cerebrospinal fluid (CSF) levels of the metabolite were continued. Development of an assay for o-methylated metabolites of norepinephrine and epinephrine in plasma and CSF was begun.